Compressor unloader



Patented Jan. 4, 1944 COMPRESSOR UNLOADER l Harley H. Bixler, Schenectady, N. Y., assignor to General Electric Company, a corporation of New York Application October 9, 1941, Serial No. 414,293

7- claims. 01.' 23o-24) My invention relates to refrigerating machines and more particularly to unloading'mechanisms for refrigerant compressors.

Refrigerating machines of the compression type include `a compressor for compressing a gaseous refrigerant, the compressor being driven by an electric motor or the like. It is desirable to provide some means for unloading the compressor during the starting period of the driving motor in order. that the motor may be subjected only to a light starting load and hence draw a relatively low starting current. It is also desirable that the unloading means should be so arranged as to unload the compressor during the period following cutting oi of electric current to the motor when the compressor is coasting4 to a stop. It is still further desirable to provide an arrangement in which the compressor is unloaded when, for any reason, the supply of lubricant to the compressor is inadequate.

It is an object of my invention to provide a new and improved unloading mechanism for refrigerant compressors or the like.

Further objects and advantages of my invention will become apparent as the following description proceeds and the features of noveltywhich characterize my invention will be pointed out with particularity in the claims annexed to and forming a part of this specification.

For a better understanding of my invention,

reference may be had to the accompanying drawing in which Fig. 1 is a side elevation partly in section illustrating a casing enclosing a motor driven compressor and Fig. 2 is a partial sectional view of the valve assembly andunloader mechanism incorporated in the unit of Fig. 1.

Referring to the,` drawing, in Fig. 1 there is provided ,a .refrigerating machine having ahermetically sealed casing' I0 of any suitable construction. -There is illustrated an upper casing section II and a lower casing section i2, the adjacent edges of these sections being welded together over a reinforcing ring I3 as indicated by the numeral I4. The casingsections are preferably made of steel and mounted in any suitable position with respect to a refrigerator cabinet, not shown. A refrigerant compressorI I5 and an electric driving motor I 6 therefor are suitably supported within the hermetically sealed casing lIII as by means of a plurality of suitably secured vertical helical springs Il. The driving motor I6 is provided with af rotor I8 which is The upper end of the `shaft is provided with a crank arm 22. The rotary movement of the crank causes a reciprocatory movement of a slide member 23 in the crosshead 24, and a reciprocatory movement of the compressor piston 25 in the main cylinder bore 2B of the compressor cylinder 21 in a well-known manner.

One end of the bore 26 of the compression cylinder 2l is closed by a suitable valve assemlbly 28 including, for example, a valve plate 23 upon which are suitably mounted an intakey valve 3D and an exhaustl valve 3|. The intake valve 30 is arranged to close an intake port 32 communicating with an intake conduit 33. The exhaust valve 3| is suitably constructed and arranged for closing a plurality of exhaust openings 34 communicating between an exhaust chamber 35 in the muiiie box 28 and the interior or bore 26 of the cylinder 21. An exhaust 36 com- `municates with the exhaust chamber 35. The -valve assembly herein illustrated and described is exemplary and any suitable desired means may be substituted.

mounted on a hollow, vertical shaft I9 within a stator. The shaft I9 pis supported in suitable upper and lower bearings 20 and 2|, respectively.

I have provided unloading means for controlling the load and unloading of the compressor which is operated by lubricant circulating in a circuit including the contacting and moving surfaces of various compressor and motor parts and a lubricant reservoir Acontained within the hermetically sealed casing Ill. In the illustrative arf rangement shown, when the motor is in operation lubricant is drawn upwardly through a conduit 31 by a lubricant pump 38 which is driven by the shaft I9 of themotor. The pump is of the rotary type and includes a pair ofy oppositely extending blades 39 which are slidably mounted in suitable slots formed in the lower end of the shaft. The lower end of the shaft and the blades rotate in a chamber formed4 by a cylindrical bore 40 in a casing plate 4i, the center of the bore being eccentric withrespect to the center ofthe shaft. As the blades rotate in the chamber 40 lubricant is drawn into the chamber through the conduit 31 and expelled undei` pressure from the chamber through an outlet opening 42 and thence -upwardly through the centraI axially extending passage 43 formed in the shaft I9 of the motor \I6. A portion of the lubricant passing upwardsure in the passage 43 passes upwardly from the chamber 45 through a passage 46 to a chamber 41 disposed at one end of the unloader 48 and which opens into the unloader cylinder bore 49.

In the illustrative form of my invention, the compressor cylinder 21 and the unloader cylinder 50 vare made as an integral structure, the axes of the bores 26 and 49, respectively, of the cylinders, being arranged in substantially parallely relationship. The unloader 48 includes an openended, preferably cylindrical, sleeve 52, and a generally cup-shaped partition member or means 5I transversely disposed with respect to the sleeve, and the member and sleeve being secured together in some suitable manner, as by welding, to form an open ended piston, the open end being directed toward the open end of the bore 49. The unloader 48 also comprises a second generally cupshaped member 53 which is secured as by means of a rivet 54 to a bracket or arm 55, the latter being suitably secured as to the mulile box or cylinder head as by means of suitably threaded fastening means 56. The cup-like members 5I and 53 are 'biased apart as by a compression spring 51, the spring normally biasing the unloader mechanism to the unloading position. In this position an aperture 58 in vthe wall of the sleeve 52 is aligned with an opening 59 extending between the cylinders 21 and 50 so `that in the unloaded position of the unloading mechanism there `is provided communicating means, as a passage, between the high compression end of the cylinder bore 26 and the open end of the sleeve 52 in one predetermined position of the piston. The cup-like member 53 is constructed and arranged with its side walls in spaced apart relation with respect to the sleeve 52 to provide a suitably proportioned opening 6I therebetween. Thus, the open end of the unloader piston provides communication between the interior ofthe casing III exteriorly of they compressoiI and the high side of the compressor mechanism. 'I'he unloaded position of the mechanism is illustrated in Fig. 2.

In operation, gaseous refrigerant is drawn through a conduit 65 and discharged into the casing I0. Gas is drawn in the compressor through the conduit 33, compressed and discharged through the conduit 36, exhaust mullier 66 and conduit 61 to a suitable condenser (not shown).

When the compressor starts up, oil is pumped to the bore 49 by. the lubricant pump 3B and passes therefrom through a sharp-edged orifice 62 in the sleeve 5 2 to a passage 63 communicating with the cylinder bore 26. 'Ihe lubricant passing through the matching openings 62 and 63 flows into an annular groove 64 disposed in the surface of the cylinder bore and an annular groove 59 in the surface of the piston for lubricating the piston. The pressure of the lubricant supplied to the unloader 48 varies directly as the speed of the lubricant pump and hence as the speed of the motor I6, and the amount of lubricant which is diverted from the. bore 49 through the orice 62 varies as the square root of the pressure. .The area of the orifice is pref- Therefore, the sleeve 52 is also moved outwardly and when the oil pressure builds up suiciently the openings or apertures 58 and 59 will be moved with respect to each other to such an extent that the passage communicating with the cylinder bore 26 is closed and the compressor is then in condition to compress the refrigerant or other Working fluid and the motor I6 will be loaded.

When the electric power to the motor is cut off, as when the refrigerating cycle is entering the off period, the lubricant pressure will de.- crease. and the force stored in the spring 51 will become effective to urge the sleeve 52 inwardly t a position in which the opening or passage 59 matches with the opening or passage 58 and hence a by-pass around the intake valve 30 is provided by the establishment of communication between the main cylinder bore 26 and the intake side of the compressor, i. e., the interior of casing I0, thereby unloading the motor. This path of communication comprises the passages 59 and 58, portion 49a of bore 49 and opening 6I to the interior of the casing. There is also a path of communication between the interior of the casing I8 by means of intake conduit 33 and port 32 around theV intake valve.v Thus as long as the motor speed is less than the predetermined amount, communication with the interior of the casing' III is maintained during both intake and exhaust strokes. Accordingly, the compressor cannot be loaded until the oil pressure acting on cup 5I causes suiiicient movement of the sleeve 52 to move passages 58 and 5 9 out of alignment.

It will be seenl that by reason of the above described construction, failure or lack of lubricant pressure at the unloading mechanism for "u any reason, will cause the motor to be unloaded.

erably proportioned so that it will divert all'of the lubricant supplied to the unloader until the motor I6 reaches a predetermined speed, as about sixty per cent full running speed. After the motor I6 reaches such predetermined speed the lubricant in excess of the amount which may be diverted through the orifice is accumulated in the bore 49 and is eective to cause the piston 5I to move outwardly in the cylinder bore.

Muiling means is provided for the gas discharged during the unloading period. When the passager59 is valved olf as the apparatus comes up to speed, the discharged working fluid, as refrigerant, will tend` to cause undesirable noise. I have provided means establishing a restricted opening of predetermined area for such discharge fluid from the unloader bore to the interior of the compressor casing, the open end of the unloader bore acting as an exhaust muiller. In the illustrated form of my invention, the opening establishing means takes the form of the cup 53, as previouslyl described. By providing the cup-like mem-bers disposed with the open ends opposite each other and a relatively long unloader cylinder bore, as shown, and by constructsleeve, as a. few thousandths of an inch, thereA results an efficient muffling action. The parts can be constructed in other ways to form a mufiler, however. If desired, guidesmay be provided on the outside of the member 53 or the inner Wall of the sleeve to accurately locate the parts and linsure uniform spacing. The guides may take the form .of a plurality of outwardly directed projections.

While I have described a particular embodiment of my invention, I do not desire my invention to be limited to the particular construction shown and described, and I intend in the appended claims to cover all modifications within the spirit and scope of my invention.,

What I claim as new and desire to secure by Letters Patent of the United States is:

1. In' a compressor having a main cylinder bore 1n which a working fluid is compressed by a piston and an unloader cylinder bore, reciprocable to the predetermined position, and means re-' sponsive to compressor lubricant pressure for causing movement of the reciprocable means to cut off communication between the cylinder bores. Y

2. In a compressor having walls deiining a main cylinder bore in which a working fluid is to be compressed by a piston and an unloader cylinl.

der bore, piston means reciprocably disposed in each of said cylinder bores, said walls having a rst passage communicating between said bores,

said unloader cylinder bore having a second passage communicating with the intake side of said compressor, movable means associated with the unloader piston means for closing said iirst passage in one position of said unloader piston means, means for biasing said last mentioned means to open said iirst passage for unloading said compressor, and means for supplying lubricant under pressure to said unloader cylinder for moving said movable means to close said nrst passage.

3. In a compressor having walls defining a main cylinder bore in which a working fluid is compressed by a piston and an unloader cylinder to a position cutting ol such communication,

means for biasing said sleeve toward the position in which said passage is open to the intake side of said compressor, and means supplying lubricant under pressure -to said unloader cylinder for moving said sleeve in a direction to close said passage.

4. In a compressor having walls defining a main cylinder bore in which a working iiuid is compressed by a main piston and an open-ended unloader cylinder bore, an unloader piston reciprocably arranged in the unloader cylinder bore, `said walls having an opening communicating between the bores, said unloader pistn having an opening adapted to be vdisposed in alignment with the first-mentionedopening in one position -of the unloader piston, a member extending into the open end of the unloader bore, said member having its outer surface spaced from the inner surface 0f Said unloader cylindervbore for providing a passage between the intake side of the com- Pressor and the opening in the piston, means for biasing lsaid unloader piston into the position in which the openings are aligned, and means responsive to compressor lubricant pressure for causing movement of the unloader piston to cut on communication between said openings.

5. In a compressor having a cylinder block including a main cylinder bore in whicha working fluid is compressed by a main piston and an unan open-ended unloader piston reciprocably arranged inthe unloader cylinder bore, the open end thereof communicating with the intake side of said compressor, said main cylinder bore hav- `ing an poening in the wall thereof, said unloader,

piston having an opening through the unloader piston wall and communicating with the open end thereof and adapted to be disposed in alignment with the first-mentioned opening in the unloaded position of the unloader piston, an open-ended member extending into the open end of the unloader piston, the open end of said member being opposed to the open, end of the unloader piston, said member being slightly smaller ment of the unloader piston in opposition to the biasing means to close the opening into the main cylinder bore.

6. In a compressor havingwalls defining a main cylinder bore in which a working tluid'is compressed by a piston and an open-ended unloader cylinder bore, a piston reciprocably` arranged in the unloader cylinder bore, said walls having an opening communicating between said bores, said unloader piston having an opening adapted to be disposed in alignment with the mst-mentioned opening in one position of the unloader piston, means closing the open end of the unloader bore, said means being arranged to provide communication between the intake side of theV compressor and the opening in the piston, means for lpiasin'g said unloader piston into the position in""which the openings are aligned, and means responsive to compressor lubricant pressure for causing movement of the unloader piston to cut oiffcommunication between said openings.

7. In a compressor having a cylinder block including a main cylinder bore in which a working iiuid is compressed by a piston and an unloader cylinder bore spaced from said main bore, a cy- -lindrical sleeve reciprocably arranged in said unloader bore, partition means transversely disposed with respect to said sleeve and secured thereto in order' to provide an open ended piston, said open end thereof communicating with the intake side of said compressor, said main cylinder bore having an opening in the wall thereof, said sleeve havingan opening through its wall and communicating with said open end of said piston, and

of said member being opposed to the said op'en end oi the piston, said member being externally shaped to provide communication between the unloader piston and the intake side of the com- I pressor, means for biasing the piston and. theV member for `moving said piston to a position' in loader cylinder bore spaced from said main' bore',

which the openings are aligned, Aand means responsive to compressor lubricant pressure' or causing movement of the piston in opposition to the biasing means to close the opening into the main cylinder bore.

\ HARLEY H. BIXLER. I 

